1. Field of the Invention
The present invention relates to an exhaust gas treating apparatus.
2. Description of the Related Art
Conventionally, as one of the automotive exhasut gas treating systems, an SCR (selective catalytic reduction) system has been known in which NOx is reduced to nitrogen and water by using ammonia.
In the system, the following chemical reactions are performed.4NO+4NH3+O2→4N2+6H2O6NO2+8NH3→7N2+12H2ONO+NO2+2NH3→2N2+3H2O
In addition, as an ammonia absorbing material, zeolite is known in the SCR system.
In JPA H9-103653, a method is disclosed in which NOx is converted into a harmless substance. In the method, Fe-ZSM-5 monolithic structure zeolite is formed in which a mole ratio of silica to alumina is at least approximately 10 and the Fe contained amount is approximately 1 to 5 wt %, and the formed zeolite is configured so as to contact a work-stream containing NOx at approximately at least 200° C.
In WO2006/137149A, a honeycomb structure is disclosed. A honeycomb unit of the honeycomb structure is formed so as to contain inorganic particles and inorganic fibers and/or inorganic whiskers. The inorganic particles are selected from one or more materials of a group of alumina, silica, zirconia, titania, ceria, mullite, and zeolite.
The entire contents of JPA H9-103653 and WO2006/137149A are hereby incorporated by reference.